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Formula: CaMnSi2O6
Inosilicate (chain silicate), clinopyroxene subgroup,
pyroxene group, forms a series with
hedenbergite and with diopside,
manganese-bearing mineral
Crystal System: Monoclinic
Specific gravity: 3.56 measured
Hardness: 6
Streak: White
Colour: Blue-green, grey-white, dark brown, colourless
Common impurities: Ti,Al,Fe,Mg,Na,K,C,P,H2O
Environments:
Metamorphic environments
Hydrothermal environments
Johannsenite is found in contact metamorphic environments,
in skarn, and less commonly in quartz
or calcite veins cutting rhyolite.
It is characteristic of metasomatised limestone adjacent to acid and
intermediate intrusions, where it is often associated with rhodonite and
bustamite. Associated minerals include
rhodonite and manganese oxides
(HOM, Dana).
Localities
There are three co-type Localities, the Temperino Mine, Campiglia Marittima, Livorno Province, Tuscany, Italy, Civillina
Mountain, Recoaro Terme, Vicenza Province, Veneto, Italy, and the Franklin Mine, Franklin, Franklin Mining District,
Sussex County, New Jersey, USA.
At the Woods Mine, Darling county, New South Wales, Australia, johannsenite has been found as radial aggregates
intergrown with serandite, quartz and
minor manganiferous aegirine. It
appears that the upper temperature limit during the metamorphosis of the Woods mine
manganese deposit was about 300
At the North Mine, Broken Hill, Broken Hill district, Yancowinna county, New South Wales, Australia, johannsenite
occurs as ferroan material with pyrosmalite-(Mn) and
bustamite
(Dana).
At Tetela de Ocampo, Tetela de Ocampo Municipality, Puebla, Mexico, johannsenite occurs in
calcite veins in
rhyolite and is altered to
rhodonite and xonotlite and
calcite
(DHZ 2A p421, Dana).
At the Franklin Mine, Franklin, Franklin Mining District, Sussex County, New Jersey, USA, johannsenite occurs
with rhodonite in interstices of
andradite-manganophyllite
breccia
(Dana).
At the Triple Trip Mine (Brown Mule Mine), Copper Creek, Mason county, Washington, USA, johannsenite occurs
as veins in rhodonite
(Dana).
Alteration
johannsenite and H2O to rhodonite and
xonotlite
6CaMnSi2O6 + H2O → 6Mn2+SiO3 +
Ca6Si6O17(OH)2
(DHZ 2A p421).
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